Treatment of cheese whey wastewater by electrochemical oxidation using BDD, Ti/RuO2-TiO2, and Ti/RuO2-IrO2-Pt anodes: ecotoxicological and energetic evaluation

Abstract

The effectiveness of boron-doped diamond (BDD) and titanium metal-mixed oxides (Ti/MMO: Ti/RuO 2 -TiO 2 and Ti/RuO 2 -IrO 2 -Pt) anodes to treat cheese whey wastewater (CWW) by electrochemical oxidation (EO) was evaluated. The results show that EO with BDD is effective in the removal of organic compounds. Conversely, Ti/MMO anodes exhibit higher removals of nitrogenated compounds. After 8 h of EO treatment at an applied current density of 500 A m −2 , the biodegradability index increased from 0.55 to 0.81 with the BDD anode, while with Ti/MMO only reached 0.64. The acute toxicity of the CWW, before and after treatment, was assessed with the model organism Daphnia magna . The use of BDD showed favorable outcomes, leading to a reduction in ecotoxicity, which changed the CWW classification from “very toxic” to “toxic,” very close to the “non-toxic” level. Contrarywise, the use of Ti/MMO anodes led to an escalation of potentially harmful substances in the treated effluent. Still, Ti/MMO anodes provide the most favorable energy consumption when operating at current densities equal to or below 100 A m −2 . While both Ti/RuO 2 -TiO 2 and Ti/RuO 2 -IrO 2 -Pt exhibit similar performance, the effectiveness of Ti/RuO 2 -TiO 2 is somewhat lower.

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